1. Field of the Invention
The present invention relates to a process for producing capsules having a permeability-controllable membrane by using a soluble chitin derivative such as chitosan as a membrane-forming material.
2. Prior Art
In the biotechnologic field, much attention has been paid to a micro-capsulation process wherein a microorganism or an enzyme is immobilized with capsules or wherein animal cells are cultured in capsules.
In the micro-capsulation process, the cells can be protected from a mechanical shearing force during the culture. Also, the permeability of the capsule membrane is controllable. Therefore, physiologically active substances produced by the cells can be accumulated at a high concentration in the capsules and the substances can be recovered in an advantageous manner. In addition, by this micro-capsulation process, the cells can be easily separated from the culture solution.
However, in the micro-capsulation process, the permeability of the capsule membrane cannot be easily controlled at a certain level. In order to resolve this problem, there has been proposed, as disclosed in Japanese Patent Unexamined Published Application (hereinafter referred to as `J.P. KOKAI`) No. 55-44387, a process for producing semipermeable microcapsules, wherein the permeability of the microcapsule membrane is controlled by adjusting a parameter in interfacial polymerization reaction during the formation of the membrane. However, this process is yet impractical, because its process is complicated and various solvents are necessitated.